Wireless Local Area Networks
Wireless local area networks (WLAN) provide wireless data connectivity to wireless client devices over a limited coverage range. Commonly known as WiFi™, the wireless networking protocol is defined by the IEEE 802.11 family of standards. The standards specify how frequencies, data rates, authentication, etc. to allow internetworking between devices from different manufacturers.
VoWiFi
A recent development is the ability for client devices to offer voice calling through the standard dialer application on mobile device. In contrast to Voice over IP (VoIP) services, the mobile device is contactable via the cellular number associated with the device via a cellular, and in particular Long Term Evolution (LTE) data network.
The VoWiFi application resides within the IMS platform and therefore can allow handover between the cellular network and VoWiFi supporting WiFi network estate. A typical handover scenario is when a user returns home and the mobile device which is connected to a macrocell of the LTE network hands over to the user's home network wireless network to maintain the same service. When the user leaves the range of their home network, then their mobile device will be configured to handover from the home WLAN to the macrocell eNodeB.
In the current implementations, only handovers from VoLTE to VoWiFi and VoWiFi to VoLTE are considered.
Although a WiFi network generated by a single Wireless Access Point may only extend for tens of meters due to transmission power constraints, it is known to configure several WAPs to have the same SSID and authentication settings to allow client devices to change physical location while still being connected to WiFi. A corporate network in a large office building is an example. Furthermore, public hotspot networks are also known whereby the access points are placed over a geographic area such as a city and configured to have the same SSID but no WLAN authentication. A centralized server carries out authentication at a higher network layer and client WiFi devices with a valid login are able to access the hotspot network wherever there is a hotspot device. An example of a hotspot network is the BT WiFi™ network. Especially in densely populated areas, the range of these hotspot WAPs may result in there being a contiguous range of WiFi connectivity such that the user can travel for a range beyond their home WiFi network and still be connected to the same WiFi hotspot network. However, for VoWiFi, the standard handover mechanisms require the VoWiFi service to handover to the VoLTE service before then handing over back to the newly connected WiFi network and VoWiFi service. This processing to switch between three different physical networks is costly in terms of time and processing power.
Similarly, if the user does not wish to use VoLTE or their device is not capable of supporting the LTE network, it is not possible to seamlessly switch between WAPs so that VoWiFi connectivity is maintained without a temporary break in service where calls and messages may be missed.